All wave distribution system



Jan. 31, 1939. v. D" LANDON 2,145,548

ALL WAVE DISTRIBUTION SYSTEM Filed Dec. 18, 1936 2 Sheets-Sheet l 3nnentor Littorneg Jan. 31, 1939. v. D. LANDON ALL WAVE DISTRIBUTION SYSTEM Filed Dec. 18, 1936 2 Sheets-Sheet 2 Gttorneg Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE Vernon D. Landon, Haddonfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application December 18, 1936, Serial No. 116,562

4 Claims.

My invention relates to all wave distribution systems, and particularly to an all wave distribution system in which a large number of outlets are supplied with high frequency energy cover- 5 ing a wide frequency range and originating from a single source.

In the distribution of radio frequency energy, it may become essential to provide means for covering a range of frequencies of the order of 100 to l; e. g., 500 kcs. to 50,000 kcs. Furthermore, in such a distributing system it is desirable to supply energy to a plurality of outlets efficiently and thereby minimize the power amplifier requirements. It is also desirable to arrange the system so that, regardless of the number of outlets in use, no unbalancing or poor regulation will occur.

One of the essential elements in an all wave distribution system, covering a wide band of fre- 20 quencies, is a transformer of extremely low leakage reactance. I have found that a bifilar wound two to one auto transformer, including a suitable magnetic core, will not only cover the desired frequency range, but may be connected to four similar two to one step-down transformers whose terminating impedances are so arranged that the effective impedance of the primary circuits of the four transformers substantially equals the output impedance of the first mentioned transformer.

I prefer to employ the bifilar winding as this type of winding minimizes leakage reactance. The use of the secondary winding as a part of the primary still further reduces the leakage reac- 35 tance. Only transformers having approximately integral ratios may be constructed with this-type of winding. I have found that a transformer ratio of 2 to 1 has the highest percentage coupling. The use of a magnetic core material such as magnetite still further increases the percentage coupling. It is by the use of all these contributing factors that the response can be maintained substantially flat over the desired band of 100 to 1 frequency ratio.

One of the objects of my invention is to provide means for efiiciently transferring radio frequency energy from a single source to a plurality of output circuits.

Another object is to efficiently transfer a very wide range of radio frequency energy from a single input to a plurality of output circuits.

A further object of my invention is to provide means for transforming radio frequency energy from a single transformer to four transformers which may in turn be connected to means for will be hereinafter described, and a metallic shield 5. The shield may be secured to the base I by suitable bolts I or the like. Connections to the transformer may be made by securing the shielding covering of incoming and outgoing leads to clips 9, II and the connecting wires to the contact lugs I3, I5, I1. I prefer to use shielded leads, which can be inserted through holes I9, 2| in the base I. The shielding of the leads may be soldered to the clips 9, I I. Although it is not essential, I prefer to design the base I so that it may be secured within a standard electrical outlet box. Mounting holes 23, 25 are provided for this purpose.

The transformer winding, considerably enlarged, is shown in Fig. 2. On a suitable insulated 3 form 21, a pair of wires 29, 3| are bifilar wound. These wires are insulated from each other by a coating of enamel or the like. The terminals of the Wires are connected to form a two to one bifilar wound step down transformer. The terminating leads are connected to the lugs I3, I5, I1. To avoid confusion in the illustration, these connections have been omitted. A pair of lugs 33, 35 are secured to the Bakelite form to provide supporting members for mounting the transformer winding on the base I. A magnetite core 3'! is secured within the Bakelite form by cement, drive fit, or the like.

By way of example, I have found that two windings of substantially ten turns each, of No. 34 enameled copper wire, wound on a Bakelite form about one inch long and A in diameter, are satisfactory. Magnetite cores of a diameter of slightly less than and approximately in length, are suitable. A transformer of this type has a very low leakage reactance, and a suitable characteristic from 500 kilocycles to 50,000 kilocycles.

The method of connecting these transformers in the distribution system illustrated by Fig. 3 is 56 as follows: The lead 31 is connected to a suitable source of radio frequency energy, such as a power amplifier or the like, which is not shown. This lead is preferably shielded by a metallic braid or conduit 39. The lead 3! is connected to the primary of the transformer 41, and the return connection from the primary to the source is made through a grounded return connection.

The secondary of the transformer consists of half of the total winding. The high potential terminal 43 of the secondary is connected through shielded leads 45, 41, 49, 51. Each of these leads 45, 41, etc., is connected to the primary circuits of four step-down transformers 53, 55, 51, 59. These transformers are bifilar wound, two to one step-down transformers of the type previously described. Each of the secondaries of these four transformers is in turn connected to four distributing leads. To avoid unnecessary repetition, only certain of the transformer connections will be described.

Considering the first transformer 53, its secondary terminal is represented by the dot 6!. This secondary terminal 6| is connected to four shielded leads 63, 65, E51, 69. Each of the last mentioned leads 63, 65, etc., may be connected to four similar two to one step-down transformers of the type described, or the several leads 53, 35, etc., may be terminated in resistors 'H, 13, 15, 11.

I have determined that a suitable terminating impedance of ohms may be used to match the impedance of the transformer and connected shielded leads. Suitable ground returns are made from each of the resistors to complete the secondary circuits of the transformer 53. Each of the resistors H, 13, etc., forms the outlet for all wave radio receiver 19 or the like. It should be understood that the several transformers 55, 51, 59, whose connections have not been described, have secondary circuits which are the equivalent of those of the transformer 53. It should also be understood that any of the transformers may be connected to four similar transformers, of the type described, instead of terminating in output resistors.

In certain installations it may be desirable to omit any one of the four transformers which make up the networks described above. In such event, the fourth connection from any given transformer should be terminated by a resistance of the order of 70 ohms, which represents the normal primary circuit impedance of any one of the transformers.

Thus I have described a two to one step-down bifilar wound shielded transformer having a magnetite core and circuit connections whereby a single source of radio frequency energy may be applied to a plurality of output resistors. The network is arranged so that a single transformer is connected to four similar transformers, and these four transformers are in turn. each connected to four more similar transformers, each of which may in turn be further connected to 7 four more transformers. In the event that any one transformer is omitted, an equivalent terminating impedance is connected in its place. With this arrangement, each of the transformers is matched to a suitable terminating impedance, which results in an efficient transfer of energy and a suitable coverage over a wide frequency range.

I claim as my invention:

1. An all wave distribution system including in combination a source of energy, a step-down transformer passing a band of frequencies of the order of me to 1 connected to said source, a plurality of similar step-down transformers connected in parallel to the output of said first mentioned transformer, and a plurality of terminating resistors each connected to the secondaries of said plurality of transformers, whereby the parallel input impedance of the plurality of transformers is substantially equal to the output impedance of said first mentioned step down transformer.

2. A radio frequency distribution system comrising a source of radio frequency energy, a bifilar wound step-down transformer having its primary connected to said source, a plurality of step-down transformers whose impedance characteristics are substantially similar to said first mentioned transformer, having primary circuits connected in parallel to the secondary circuit of said first mentioned transformer, and a plurality of terminating resistors each connected to the secondary circuits of the plurality of transformers, whereby the secondary impedance of the first mentioned transformer is matched by the parallel primary connection of said plurality of transformers.

3. A radio frequency distribution system including, in combination, a source of radio frequency energy, a main transmission line connected to said source, and a plurality of similar bifilar wound step-down auto transformers connected so that the secondary of one transformer is connected to the paralleled primaries of a number of succeeding transformers which is substantially equal to the square of the ratio of the number of-primary turns divided by the number of secondary turns of said transformers.

i. In a distribution system of the character described, means for transferringa wide band.

of radio frequency energy from an input source to a plurality of receiver coupling transformers, said means comprising a plurality of transformers, each designed to transfer radio frequency energy covering a frequency range of the order of to l, and having a two to one step-down ratio, in which each transformer intermediate said source and said receiver coupling transformers is connected to the paralleled primaries of four succeeding transformers, and in which the secondaries of said receiver coupling transformers are connected to resistors each substantially equivalent to the impedance of four primaries in parallel.

VERNON D. LANDON. 

